The present invention relates to an image formation apparatus such as copying machines, printers, and plotters.
As the output apparatus of computers and work stations, there are known ink-jet type image formation apparatuses which form images by ejecting an ink onto a recording medium like a recording paper sheet, and electrophotography type image formation apparatuses which forms images by use of a developing agent on a recording medium. Some of such image formation apparatuses have an insertion port for inserting a recording medium and a discharge port for discharging the recording medium on the same side, and have a passage for introducing the recording medium to the insertion port on the same side as the ports. Some of the image formation apparatuses have a detection sensor near the insertion port for detecting the recording medium to measure the length of the recording medium in formation of the image on the recording medium.
Such an image formation apparatus having the aforementioned passage and the detection sensor measures the length of the recording medium by detecting with the sensor the front end of the recording medium inserted through the passage and the insertion port, delivering further the recording medium toward the discharge port, and detecting with the sensor the rear end of the recording medium. Thus the length of the recording medium is measured by detection of the front end and the rear end of the recording medium by the detection sensor. After the length measurement of the recording medium by detection of the front end and the rear end, the recording medium is delivered back from the discharge port toward the insertion port (in the direction reverse to the length measurement direction), thereby the recording medium is set in a standby state for printing.
However, in the case where the discharge port is placed above the insertion port and the recording medium is long, the recording medium may hang down from the discharge port to come close to the passage at the time when the length measurement is completed by detection of the rear end of the recording medium delivered through the passage and the insertion port. After the length measurement, the recording medium is sent back in the direction reverse to the length measurement to be ready for printing. In this state, the rear end portion of the recording medium may reach the passage. Thereby, the rear end of the recording medium may be brought into contact with the front end thereof, and may be wound by the front end to introduce the rear end into the discharge port to cause paper jamming undesirably. Such jamming can occur even with the insertion port placed above the discharge port, if the rear end portion of the recording medium hangs down.
Furthermore, some of the ink-jet type or the electrophotography type of image formation apparatuses have the insertion port for inserting the recording medium and the discharge port for discharging the recording medium on the same side, and additionally an insertion table on the same side for introducing the recording medium into the insertion port.
For inserting the recording medium into the insertion port for delivery, the recording medium is laid on the insertion table, and is introduced therefrom into the insertion port. A detection sensor is placed near the insertion port to detect the recording medium. On detection of the front end of the recording medium by this detection sensor, the delivery roller starts to deliver the recording medium.
Some of the image formation apparatuses having the insertion table and the detection sensor as mentioned above form the image on the recording medium after measurement of the sheet length of the recording medium. In such an image formation apparatus, the recording medium is introduced from the insertion table into the insertion port; the front end of the recording medium is detected by the sensor; the recording medium is delivered toward the discharge port; and the rear end is detected by the sensor. In such a manner, the length of the recording medium is derived by detection of the front end and the rear end. The recording medium after the length measurement is delivered back from the discharge port toward the insertion port (in the direction reverse to the length measurement) to be set in a standby state for printing.
However, in the case where the discharge port is placed above the insertion port and the recording medium sheet is long, the front end portion of the recording medium may possibly hang down from the discharge port onto the insertion table and may be inserted again into the insertion port to cause paper jamming. Such jamming is liable to be caused in image formation on a long sheet of the recording medium.
Such jamming can be prevented by providing a guide or a like member to lead the recording medium discharged from the discharge port to be isolated from the insertion port.
However, if the recording medium curls as a whole or the front end thereof is curled by moisture absorption or another cause, the recording medium, which is discharged from the discharge port to a position distant to the insertion port, can hang down onto the insertion table again and be drawn into the insertion port to cause jamming.
The present invention intends to provide an image formation apparatus which does not cause paper jamming, under the above situations.
A first embodiment of the image formation apparatus of the present invention for achieving the above object, has an insertion port for inserting a recording medium and a discharge port for discharging the recording medium provided on the same side, and a first passage for guiding the recording medium to the insertion port also on the same side as above, wherein
(1) the apparatus has a second passage provided on a side opposite to the discharge port relative to the first passage and communicating with the insertion port.
(2) The first passage and the second passage preferably join together near the insertion port, and
(3) an intercepting member is preferably provided which intercepts the communication between the first passage and the insertion port at a prescribed timing to allow the insertion port to communicate only with the second passage.
A second embodiment of the image formation apparatus of the present invention for achieving the above object has an insertion port for insertion of a recording medium and a discharge port for discharging the recording medium provided on the same side, and an insertion table for guiding the recording medium to the insertion port also on the same side as above, wherein
(4) the insertion table has a stair at the border between a portion near to the insertion port and an adjacent portion distant from the insertion portion, and
(5) the apparatus has preferably a blocking member for blocking the space communicating with the insertion port at a prescribed timing at or around the stair.